Children with Attention-Deficit/Hyperactivity Disorder (ADHD) participated in double-blind placebo-controlled randomized trails of stimulants while undergoing anatomic imaging with magnetic resonance imaging (MRI). Girls with ADHD are showing similar basal ganglia abnormalities to those seen in our previous study of boys. These subjects and others also participate in studies of the genetics of ADHD using case-control, family association, and affected-sibling methods. Preliminary findings do not support abnormalities in the D4 receptor or the dopamine transporter genes. The first controlled comparison in girls of dextroamphetamine and methylphenidate was completed. A pilot study comparing detroamphetamine to a re-marked amphetamine (Adderall) in a placebo-controlled randomized trail has also been completed (n=10). Currently, subjects participate in a controlled trail of regular-release dextroamphetamine, long-acting dextroamphetamine, Adderall and placebo.